The present invention relates to apparatus for dispensing high viscosity thermoplastic materials from drums or other bulk shipping containers.
The apparatus of the present invention is useful for dispensing a variety of high viscosity thermoplastic materials such as resins, sealants and adhesives. Typical of such materials ordinarily shipped or stored in bulk shipping containers are the hot melt adhesives. Hot melt adhesives are an art recognized class of adhesives which may be defined as 100% solids thermoplastic materials which typically are solids at room temperature. Prior to use they are melted by heating, usually to 150.degree.-200.degree. C., and they are then applied to a substrate in their molten state. On cooling, they solidfy, thereby producing a bond.
Despite a long recognized need for effective systems for removing or dispensing such materials from the containers in which they are stored or shipped (such as, for example, 55-gallon drums), the commercially available systems have not proven to be entirely satisfactory for all applications. For example, U.S. Pat. No. 3,637,111 describes a heating and pumping system which requires the material to be heated into a substantially liquid state before it is pumped by a conventional pump such as a standard Pyles drum pump. Such a system would not be useful with those materials which do not convert into a substantially liquid state at practical temperatures. Furthermore, where the material is not to be used immediately, or could be used at a lower temperature than required to obtain a substantially liquid state, additional heating expenses are unnecessarily incurred by such a system in converting the materials into the substantially liquid state. Also, because of the time required for such a system to liquify the material, as a practical matter limits are imposed upon the speed with which the system can unload the material from the storage or shipping container. Finally, such a system cannot be used with materials which cannot be subjected to high shear forces of the type produced by a conventional pump.
Accordingly, it is an object of the present invention to provide apparatus capable of dispensing high viscosity thermoplastic materials without heating them into a substantially liquid state, thereby saving on heating costs and increasing the dispensing speed.
Another object is to provide such an apparatus which is useful with a wide variety of materials including those which cannot be subjected to high shear and those which do not assume a substantially liquid state at practical temperatures.
A further object is to provide such an apparatus which is inexpensive to manufacture, of sturdy construction, and easily operable.